Gasket with two concentric lips

ABSTRACT

A gasket, sliding about the axis of rotation of a part to be brought closer to or to be spaced apart from another part with which it provides tightness through a pair of lips provided on a ring. The gasket includes a portion of the ring capable of bending to modify the clearance between the corresponding lip and the part, the pressure prevailing in an intermediate cavity, the balance of forces on the joint and hence the clearance and the leak flow rate allowed before the gasket, which is advantageous in particular in a case of ventilation gas for refrigerating an element of the machine in controlled operating conditions.

The purpose of this invention is a gasket placed between two mutuallyrotating parts, and more precisely of the sliding type on one of theparts along the rotation axis and comprising two concentric lipsdirected towards a plane face of the other of the parts.

This type of gasket creates a variable leak tightness between twochambers delimited by two parts depending on the clearance between thelips and the plane face, and can be in different equilibrium statesdetermined by the forces of the different pressures applied to thesurface. The lips play the important role of delimiting a cavity inwhich there is an intermediate pressure between the pressures in the twochambers separated by the gasket. This intermediate pressure depends onthe clearance between the lips and the plane face of the part facing it;for example, if this clearance increases, leaks through the gasketbecome greater and the pressure in the cavity tends to approach thelowest pressure. The pressure balance is broken since the pressureforces acting in the cavity and pushing the gasket from the plane faceare lowered, while the other pressure forces remain the same. Therefore,the gasket is pushed towards the plane face until the clearance returnsto its equilibrium value. Therefore there will not be any frictionbetween a well-designed gasket of this type and the plane face, and itwill only allow very small flows of gas through it.

However, the stability of the equilibrium may still become adisadvantage in some circumstances, particularly when the gas in thehigh-pressure chamber is a ventilation gas for which the leak flowtowards another chamber must be increased so as to add further coolingto it.

Consequently, the purpose of this invention is an improvement to thegasket described above so that its clearance and its leak flow can bevaried deliberately and under control. The means selected consists ofallowing deformation of one of the portions of the gasket supporting oneof the lips, to move away from or towards the plane part and tofacilitate or oppose communication of the cavity towards the chamberbehind this mobile lip. The pressure in the cavity, and the pressureequilibrium that is found for another position of the gasket requiring aclearance and a different leak flow, are modified accordingly.

There are deformable gaskets under the pressure of the surrounding gas,but they are used in different situations and particularly do notprovide any information about how to change the pressure in a cavityintermediate between the chambers. Examples are given in European patent0 629 798 and French patent 2 765 653.

The nature of the forces causing deformation of the ring may bedifferent, as will be seen later.

Thus, the invention relates to a gasket placed between a first partprovided with a pair of circular and plane facets (or sealing areas),and a second part rotating with respect to the first part in front ofthe facets about an axis, the gasket comprising a cylindrical sleevesliding on the second part in the axis, a ring fixed to the sleeve andtwo circular lips projecting from the ring towards the facets,characterized in that the ring comprises a portion that is flexibleunder the effect of surrounding forces, between the sleeve and one ofthe lips.

The invention will now be described with reference to the figures.

FIG. 1 shows a general view of the gasket conform with the invention,and

FIGS. 2 and 3 illustrate two variant embodiments.

The gasket is marked as general reference 1 and is composed of acylinder sleeve 2, a circular ring 3 adjacent to the sleeve 2 and twosealing lips 4 and 5 projecting from the ring 3 on its face opposite thesleeve 2; it is connected in rotation to a part 6, that includes asleeve 7 in which the sleeve of the gasket 1 can slide through a packing8 that creates a secondary leak tightness. The gasket 1 also includes arotation stop pin 9 that is retained in a groove 10 of the part 6 inorder to keep them together against rotation movements, and it may becontinuous or composed of adjacent arc sectors, as is known in standardpractice.

A second part 11 supports a plane face 12 comprising a pair of polishedor mat bearing surfaces, 13 and 14 respectively, in front of the lips 4and 5; there is also a hook 15 that extends beyond the ring 3 and capsits outer periphery, to prevent excessive withdrawal movements of thegasket 1, which are always possible in transient operating phases of themachine on which it is fitted. Parts 6 and 11 rotate with respect toeach other about an axis X.

A high pressure chamber 16 is included between parts 6 and 11 and thelip 5, and a low pressure chamber 17 between the same parts 6 and 11 andthe other lip 4; finally, a cavity 18 is delimited by the ring 3, thelips 4 and 5 and the plane face 12 of the part 11.

A leakage current is maintained from the chamber 16 to the chamber 17through the clearance between the lips 4 and 5 and the bearing surfaces13 and 14; an intermediate pressure appears in the cavity 18 and itsvalue may be modified by drillings 19 through the ring 3 to set up anadditional link with one or other of the chambers, in this case the highpressure chamber 16.

As shown in FIG. 2, the ring 3 is thinned on the side of the highpressure chamber 16 and the lip 5, so as to create a flexible portion20. By adjusting the high pressure in the chamber 16 so as to increaseit, the part 20 bends towards the plane face 12 and reducescommunication with the high pressure chamber 16, and therefore the leakflow. Conversely, a reduction in the high pressure in the chamber 16increases this flow.

FIG. 3 shows an equivalent design, however in this case it is not apressure adjustment that controls deformation of the leak flow, but achange to the temperature; the flexible part, in this case reference 21,of the ring 3 (as before located between the sleeve 2 and the lip 5) iscompleted by a layer 22 of heterogeneous material that creates abimetallic structure, and therefore that has the property of bending dueto differences in the coefficients of expansion. The same effect couldbe obtained with a shape memory material worked to have two differentbending states; this material may be added onto the surface of thegasket 1, like layer 22, bonded to gasket 1; or the gasket 1 may itselfbe made from this material.

It is generally advantageous if the sleeve 2 is connected to the ring 3at a location at which the radius is not equal to average radius of thering and dividing it into two portions with unequal widths, and theflexible portion corresponds to the widest measured part starting fromthe sleeve 2.

1. A gasket configured to be arranged between a first part provided witha pair of circular and plane facets and a second part configured torotate with respect to the first part and in front of the facets aboutan axis, the gasket comprising: a cylindrical sleeve configured to slideon the second part along the axis; a ring fixed to the sleeve and twocircular lips projecting from the ring towards the facets, wherein thering comprises a portion that is flexible under effect of surroundingforces, between the sleeve and one of the lips, and the sleeve isattached to the ring away from a mean radius of the ring, the sleevedividing the ring into two portions of unequal width, the flexibleportion included in a first portion having a greater width than a secondportion.
 2. The gasket according to claim 1, wherein the flexibleportion corresponds to a thinning of the ring.
 3. The gasket accordingto claim 1, wherein the flexible portion comprises a heterogeneous partwith a portion complementary to the ring.
 4. The gasket according toclaim 3, wherein the heterogeneous part is made from a shape memoryalloy.
 5. The gasket according to claim 3, wherein the flexible portionis bimetallic.
 6. The gasket according to claim 1, wherein the gasket ismade from a shape memory alloy.
 7. The gasket according to claim 1,wherein drillings pass through the ring.
 8. The gasket according toclaim 7, wherein drillings pass through the first portion of the ring.9. A gasket configured to be arranged between a first part provided witha pair of circular and plane facets and a second part configured torotate with respect to the first part and in front of the facets aboutan axis, the gasket comprising: cylindrical sleeve means for sliding onthe second part along the axis; a ring fixed to the sleeve means and twocircular lips projecting from the ring towards the facets, wherein thering comprises means for flexing under effect of surrounding forces,between the sleeve means and one of the lips, and the sleeve means isattached to the ring away from a mean radius of the ring, the sleevemeans dividing the ring into two portions of unequal width, the meansfor flexing included in a first portion having a greater width than asecond portion.
 10. The gasket according to claim 9, wherein the meansfor flexing is a thinning of the ring.
 11. The gasket according to claim9, wherein the means for flexing is a heterogeneous part with a portioncomplementary to the ring.
 12. The gasket according to claim 11, whereinthe heterogeneous part is made from a shape memory alloy.
 13. The gasketaccording to claim 11, wherein the means for flexing is bimetallic. 14.The gasket according to claim 9, wherein the gasket is made from a shapememory alloy.
 15. The gasket according to claim 9, wherein drillingspass through the ring.
 16. The gasket according to claim 15, whereindrillings pass through the first portion of the ring.
 17. A gasketconfigured to be arranged between a first part provided with a pair ofcircular and plane facets and a second part configured to rotate withrespect to the first part and in front of the facets about an axis, thegasket comprising: a cylindrical sleeve configured to slide on thesecond part along the axis; a ring fixed to the sleeve and two circularlips projecting from the ring towards the facets, wherein the ringcomprises a portion that is flexible under effect of surrounding forces,between the sleeve and one of the lips, and the flexible portioncomprises a heterogeneous part with a portion complementary to the ring.18. The gasket according to claim 17, wherein the heterogeneous part ismade from a shape memory alloy.
 19. The gasket according to claim 17,wherein the flexible portion is bimetallic.
 20. The gasket according toclaim 17, wherein drillings pass through the ring.